In my previous patents I disclosed a device for taking blood samples from patients by the use of evacuated containers attached through a connector which could be joined to a body holding a metal cannula. The body holding the metal cannula was referred to as a support portion and was fitted with a valve which was normally closed but which opened on making connection between the support portion and the connector to the evacuated container.
While the possibility of using the support portion for the introduction of medication into a patient was disclosed, the technique by which such introduction was to be effected was not such as to make it convenient to allow the cannula to remain in the vein of a patient for periods as long as several days. In view of the fact that procedures requiring the presence of a cannula or a catheter in the vein of a patient for extended periods are now becoming common, it is evident that there is a need for a device by which such procedures can be carried out conveniently, effectively and safely. The device should make it easy to change and control the fluids being fed to the patient and should also be relatively inexpensive. Further, it would be desirable that said support portion be useable in the manner disclosed in my previous patents, namely, for taking of one or more blood samples without repeated puncture of the individual.
A most important point is the present techniques for introducing fluid into a vein or other blood vessel require connection of a source of fluid to a cannula after emplacement of the cannula in the blood vessel. Under such circumstances there is always some loss of blood from the maximal end of the cannula, an undesirable feature.